Engine starter drive



All@ 5 1952 n.1.. MILLER 2,605,642

ENGINE STARTER DRIVE Filed June 25, 1951 A @Wh/Waller W1TNEss=- om 5 AORNEY Patented Aug. 5, 1952 Bonald L Miller; Horseheads; N. Y.,assignorto endixAviat-ion.Corporation, a corporaton'of Belaware yApplication J une. 25, 19

3 Claims.

The present irnfention relatesU to an engine startern drive and moreparticularlyto an automatically meshing gearing having a yieldingselftight'ening clutch connection which is' arranged to releaseandbverrun' with a controlled amount of frictional drag when the enginestarts. v

' the types` of starting equipment in which engagement of the gearing isconsequent to the-energization of the starting'motor; it is desirable todeiinitely limit the peak torque load on the drive in order` to obvatethe necessity of using factors of safety higher than required for thenormal cranking operation.

It is* also desirable tof control rthe amount of torque transmittedbackl throughthe pinionA when the engine starts, in order to slow downthe def meshing action and prevent the pinion from being demeshedby'sporadicfiring of the engine while insuring reliable demeshi'ngaction when-the engine is trulyself-operat-ive. Y

"It-isj an object of thepresent invention to pro- Vvide a novelstarter-drive in which'a single frictional connectionservesto performboth the above statedfunctions.

It is another object to provide such a device incorporating furthermeans for insuring proper `meshing of the gearing when the startingmotor is energized.

It is another object to provide such a device which is a self-containedunit of small diameter but having adequate rotational inertia to insuresatisfactory meshing operation. f

Further objects and advantages will be apparen from the Ifollowingdescription taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevation partly in section of a preferred embodimentof the invention showing the parts in normal or idle position;

Fig. 2 is a similar View showing the parts in cranking position; and

Fig. 3 is a detail in perspective of the sleeve member and clutchelements shown disassembled.

In Fig. 1 of the drawing there is illustrated a power shaft I on which ahollow shaft 2, which is threaded for a portion of its length as shownat 3, is xedly mounted in any suitable manner as by means of a cross pin4. A pinion 5 is slidably mounted on the power shaft I beyond the end ofthe screw shaft 2 for longitudinal movement into and out of mesh with agear 6 of the engine to be started. l

A control nut 1 is threaded on the screw shaft 2, and a sleeve 8 (Fig.3), is slidably mounted at one end on the control nut and is providedwith slots 9 which receive projections II extending radially 51, serialNo. 233,42@k

(Cl.v 744-7) 2 'from the'control nut so as to form asplined connectionbetween the control nut and sleeve. A portion I2 of the sleeve near. itsopposite end is enlarged so as to form an internal shoulder I3,

- and is arranged to bear slidably on a radial flange I4 formedon theend of the screw shaft.

A conical expander ring I5 is anchored on the end of the sleeve 8y bymeans of a lock ring I6, a second expander ring I1 is slidably mountedon the sleeve, and a pair of cylindrical clutch shoes I8, IS are mountedon the sleeve between the expander', rings and. formed with flared endsto correspondwith the `conical surfaces of said rings. Means forpreventing rotation of the clutch shoes andexpander rings on the sleeveis provided in the formof keys orspline'sl yand 22 rigidly mounted orformed on .theperipheryof the Venlarged portion I2I of thesleeve,between the clutch shoes I8, I-l',l and entering `slots Zin the expanderrings so as to splinethem to the sleeve.

Albarrel member anchoredV at one end. to the pinion as shown at.24.,.s'urrounds the sleeve and clutch members and bears at its otheryend on the projections II of. thecontrol nut 1, beingretained thereonbyaflock ring 25.

Means are-provided for' transmitting pressure from the control nut tothe expander ring I1 to cause the rings to force the clutch shoes intofrictional engagement with the interior of the barrel 23. As here shownthis means comprises a spacing ring 26 slidably mounted on the sleeve inposition to be engaged by the projections I I of the control nut, and aheavy compression spring 21 located between the spacing ring and theexpander ring I1. The spacing ring 2B is yieldingly held separated fromthe control nut 1 as shown in Fig. 1 by means of a light mesh-enforcingspring 28 which rests at its ends on the spacing ring and control nut.

Means normally holding the drive in idle position is provided in theform of an anti-drift spring 29 located between the flange Ill of thescrew shaft and an interior shoulder 3l formed in the sleeve.

1n operation, starting with the parts in the positions illustrated inFig. 1, rotation of the power shaft in the direction of the arrow acauses the control nut 1 to be traversed to the right on the threads 3of the screw shaft 2, which movement is transmitted through themesh-enforcingspring 28, spacing ring 25 and clutch spring 21 to theexpander ring I1. This pressure causes the clutch shoes I8, I9 to engagethe interior of the barrel, and is also transmitted through the expanderring I5 and lock 3 ring I6 to the sleeve 8, the end of which bearsagainst the anchorage of the barrel 23 with the pinion 5, thereby movingthe pinion into mesh with the engine gear 6.

If a tooth of the pinion abuts against a tooth of the engine gear, themesh-enforcing spring 28 yields and provides a time interval duringwhich the torque will be built up suiciently to index the'pinion teethinto registry with the tooth spaces of the engine gear.

The meshing movement of the spring 28 and its associated parts islimited by engagement of the shoulder I3 of the sleeve with the stopflange I4 of the screw shaft, a thrust ring 32 being preferablyinterposed therebetween. The continued movement of the control nut 1causes it to engage the spacing ring 26 after compression of the meshenforcing spring 28, whereupon the clutch spring 21 transmits increasedpressure to the expander ring I1 causing the clutch shoes I8, I 9 tofrictionally engage the interior of the barrel 23 for transmittingcranking torque to the pinion. The pressure of the spring 21 is limitedby the engagement of the projections II of the control nut against thebottoms 33 of the slots 3 in the sleeve 8. The torque capacityrof theclutch is thus limited to a predetermined value, above which the clutchslips and thereby protects the drive from excessive stresses.

When the engine starts, the acceleration of the pinion 5 by the enginegear causes the control nut 'I to thread itself back along the screwshaft 2. The rst effect of this movement is 'to relieve the pressure onthe clutch spring 21 and therefore reduce the frictional engagement ofthe clutch shoes with the interior of the barrel. Sudden accelerationsof the pinion by sporadic explosions of the engine therefore cause theclutch members to slip and allow the pinion and barrel to overrunWithout becoming completely demeshed. When the engine becomes trulyself-operative, however, the continued rotation of the pinion and barrelis transmitted as a frictional drag to the sleeve 8 which drag isincreased by the action of centrifugal force on the clutch shoes I8, I9as the speed of rotation increases. This rotation is transmitted throughthe sleeve to the control nut 1 causing it to thread itself back to idleposition where it is maintained by the action of the anti-drift spring29.

Although but one form of the invention has been shown and described indetail it will be understood that other embodiments are possible andthat changes may be made in the design and arrangement of the partswithout departing fromthe spirit of the invention.

I claim:

1. In an engine starter drive a power shaft, a screw shaft, Xed thereon,a pinion slidably journalled on the power shaft for movement into andout of mesh with a member of an engine to be started, a control nutthreaded on the screw shaft, a sleeve having a splined connection withthe control nut, a conical expander ring anchored on the end of thesleeve, a second expander ring splined to the sleeve, a plurality ofclutch shoes non-rotatably mounted on the sleeve between the expanderrings, a barrel member surrounding the clutch shoes, anchored to thepinion at one end and bearing on the control nut at the other, means forlimiting the longitudinal movement of the sleeve, and means including a,compression spring between the control nut and the second expander ringfor causing the expander rings to force the clutch shoes into frictionalengagement with the in-V terior of the barrel. y

2. An engine starter drive as set forth in claim 1 in which the sleeveis provided with a stop for arresting the meshing movement of thecontrol nut, thereby limiting the compression of said spring, andconsequently limiting the pressure of the clutch shoes against theinterior of the barrel.

3. An engine starter drive as set forth in claim 1 in which the lastmentioned means includes a spacing ring between the control nut andcompression spring, and a mesh-enforcing compression spring seated onthe control nut and spacing ring normally holding them apart.

DONALD L. MILLER.

No references cited.

